2. This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, LP (QP), Special Situations Private Equity Fund, L.P. (PE), Special Situations Technology Fund, LP (TN) and Special Situations Technology Fund II, L.P. (T2), respectively. 274,799 shares of Common Stock are held by QP, 95,958 shares of Common Stock are held by PE, 31,111 shares of Common Stock are held by TN and 198,363 shares of Common Stock are held by T2. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, PE, TN and T2 is limited to the extent of his pecuniary interest.

Austin W. Marxe

09/28/2012

David M. Greenhouse

09/28/2012

** Signature of Reporting Person

Date

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person,
see
Instruction
4
(b)(v).